Video compression is becoming a requirement of many electronic devices. Video compression is an important component in devices such as personal computers, digital cameras, digital video cameras or camcorders, and personal video recorders (PVRs), also known as digital video recorders. To better understand how an why compression is becoming more commonplace, review of the history of how consumers view and use television signals is instructive.
Historically, television signals were broadcast from a transmitter and received and displayed immediately upon receipt on a television receiver. As television evolved, cable television became widespread. However, with the advent of cable television, viewers still watched television shows as they were broadcast. With the introduction of the video cassette recorder (VCR), television viewers were able to record television broadcasts to be viewed at a time after the original broadcast of the particular television program. This provided television viewers a greater freedom to enjoy the television broadcasts at their convenience.
Relatively recently, PVRs had been made available to consumers. PVRs including the functionality provided by TiVo, Inc. of Alviso, Calif., and Replay TV/Sonicblue, Inc. of Santa Clara, Calif., now allow the television viewer even more options as to how and when a television program or other video content will be viewed. Among other things, PVRs allow a television viewer to pause a live broadcast of a program while, for example, answering the telephone or attending to some task in the viewer's home. In addition, PVRs may include technology which records specific programs selected by a viewer from a program guide and may also include smart technology which automatically records programs meeting criteria selected by a viewer while the viewer is not available or not watching television. Generally, a PVR must receive a television broadcast and store it in a format which later will be displayed to the television viewer. Such storage must also occur in real time while the viewing of a currently live broadcast program is paused. To efficiently store broadcast programs, programs are compressed prior to storage. Similarly, other personal electronic devices compress sequences of real time images before storing them as video.